linux-kernel - [RFC][PATCH] HACK: usb: dwc2: Workaround case where GOTGCTL state is wrong

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Date:   Tue,  6 Dec 2016 17:47:58 -0800
From:   John Stultz <john.stultz@...aro.org>
To:     lkml <linux-kernel@...r.kernel.org>
Cc:     John Stultz <john.stultz@...aro.org>,
        Wei Xu <xuwei5@...ilicon.com>,
        Guodong Xu <guodong.xu@...aro.org>,
        Amit Pundir <amit.pundir@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        John Youn <johnyoun@...opsys.com>,
        Douglas Anderson <dianders@...omium.org>,
        Chen Yu <chenyu56@...wei.com>,
        Kishon Vijay Abraham I <kishon@...com>,
        Felipe Balbi <felipe.balbi@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org
Subject: [RFC][PATCH] HACK: usb: dwc2: Workaround case where GOTGCTL state is wrong

Hey John,
  Just wanted to send this by you, as it seems something is
slightly off with the GOTGCTL state when removing a otg adapter
cable. The following seems to work around the issue I'm seeing.

Let me know if you have any thoughts on this.
thanks
-john


When removing a USB-A to USB-otg adapter cable, we get a change
status irq, and then in dwc2_conn_id_status_change, we
erroniously see the GOTGCTL_CONID_B flag set. This causes us to
get  stuck in the "while (!dwc2_is_device_mode(hsotg))" loop,
spitting out "Waiting for Peripheral Mode, Mode=Host" warnings
until it fails out many seconds later.

This patch works around the issue by re-reading the GOTGCTL
state to check if the GOTGCTL_CONID_B is still set and if not
restarting the change status logic.

I suspect this isn't the best solution, but it seems to work
well for me.

Feedback would be greatly appreciated!

Cc: Wei Xu <xuwei5@...ilicon.com>
Cc: Guodong Xu <guodong.xu@...aro.org>
Cc: Amit Pundir <amit.pundir@...aro.org>
Cc: Rob Herring <robh+dt@...nel.org>
Cc: John Youn <johnyoun@...opsys.com>
Cc: Douglas Anderson <dianders@...omium.org>
Cc: Chen Yu <chenyu56@...wei.com>
Cc: Kishon Vijay Abraham I <kishon@...com>
Cc: Felipe Balbi <felipe.balbi@...ux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: linux-usb@...r.kernel.org
Signed-off-by: John Stultz <john.stultz@...aro.org>
---
 drivers/usb/dwc2/hcd.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/dwc2/hcd.c b/drivers/usb/dwc2/hcd.c
index 143da47..6d6802a 100644
--- a/drivers/usb/dwc2/hcd.c
+++ b/drivers/usb/dwc2/hcd.c
@@ -3203,7 +3203,7 @@ static void dwc2_conn_id_status_change(struct work_struct *work)
 	dev_dbg(hsotg->dev, "gotgctl=%0x\n", gotgctl);
 	dev_dbg(hsotg->dev, "gotgctl.b.conidsts=%d\n",
 		!!(gotgctl & GOTGCTL_CONID_B));
-
+again:
 	/* B-Device connector (Device Mode) */
 	if (gotgctl & GOTGCTL_CONID_B) {
 		/* Wait for switch to device mode */
@@ -3219,6 +3219,9 @@ static void dwc2_conn_id_status_change(struct work_struct *work)
 				 dwc2_is_host_mode(hsotg) ? "Host" :
 				 "Peripheral");
 			usleep_range(20000, 40000);
+			gotgctl = dwc2_readl(hsotg->regs + GOTGCTL);
+			if (!(gotgctl & GOTGCTL_CONID_B))
+				goto again;
 			if (++count > 250)
 				break;
 		}
-- 
2.7.4